Die lapping machine



y 30, 9 3- a. H. SITTNER DIE LAPPING MACHINE Filgd Oct. 20. 1931 flll- 7 fl \\/V// U Ihvehtcr; Geovge H. Sitthen H is Attorne Patented May 30, 1933 GEORGE E. SITTNER, OF SCHENECTADY, NEW YORK, ASSIGNOR T GENERAL ELECTRIC COMPANY A CORPORATION OF NEW YORK DIE LAPPING- MACHINE Application filed October 20, 1931. Serial No. 569,976.

In drawing wire from a larger to a smaller size, diamond dies, as well as those made of certain special metals, are employed. The outstanding requirement of wire drawing is that the dies shall be properly sized and shaped. The dies wear in use and have to be refinished. Some of the principal results of wear on the die are as follows: The entrance or approach angle becomes too great or too small; the length of the land becomes too great, and the formation of grooves or rings immediately preceding the land. After a die is worn, it can only be refinished for use with a large size of wire. The matterof refinishing dies is one that calls for extreme accuracy.

The object of my invention is the provision of an improved machine whereby new or worn dies may be accurately lapped or finished to predetermined dimensions, angles,

etc., and this at a reasonable cost both for the machine itself and for the lapping operation.

For a consideration of what I believe to be novel and m 1 invention attention is directed to the accompanying description and the claims appended thereto.

In the attached drawing which is illustrative of my invention, Figs. 1 to 4 illustrate worn dies; Fig. 5 illustrates a properly formed die for drawing copper wire; Fig. 6 is a view partly in elevation and partly in section of my improved lapping machine; Fig. 7 is a sectional view of the upper part of the machine showing the use of a quill for removing grooves or rings in approach portion of a die, and Fig. 8 is a detail view gauge for setting the polishing element.

In Fig. 1 is shown a die which was so shaped originally or has been so worn that the approach angle is too great, meaning thereby the angle 7. In Fig. 2 is shown a die which was so shaped originally or hasbeen so worn that the approach angle is too small. In Fig. 8 is illustrated a die in which the land 8 is too long due to wear or otherwise. Tn Fig. l is shown a die which has become grooved or ringed at 9. The foregoing, while not necessarily illustrating all forms of misshapes and wear, will serve as an indication ofsuch conditions. In Fig. 5 is shown a die which is properly shaped and dimensioned for drawing one size of copper wire. From this figure and the printed. data it will be evident that the various parts of the surface of a die must be carefully finished to size and shape if the best results are to be obtained.

Referring now to Fig. 6 which is illustrative of my improved lapping machine, 10 indicates a suitable base that is adapted to be bolted to a support. Rising from thebase is an enclosing casing 11 that also forms the frame of the machine. Located in the upper part of the frame is a die holder or support comprising a ring or carrier 12 which is mounted to revolve in suitable bearings. The ring is bored centrally to receive a disk-like member 14L which has a shouldered recess on one side to receive and retain the die holder 15 and its contained die 16. The member 14:

and. die holder 15 are held in place by flanged nuts 17, one on each side, there being one or more washers 18 located at one side of the die holder. These washers engage a nut near their outer edge and nearer the center engage the die holder. By these means, the die is securely held in place, yet can easily be removed by unscrewing one of the nuts.

Surrounding the ring or carrier 12 is a gear 19 which is driven from below as will appear later. Situated on opposite sides of the gear are sheaves or rings 20 each having a grooved face in which are located guide rollers 21 each mounted on short shafts 22 supported by the frame. These rollers, of which there are three on each side, displaced by 120, serve as bearings for the revolving die carrying parts and. also serve to hold the parts against sidewise movements. The gear and grooved rings are secured to the ring or carrier 12 by a key 23.

The ring or carrier 12 is rotated at a suitable speed, say of the order of 1200 R.P.M. by means of a spur gear 25 mounted on a cross shaft 26, the latter having bearings supported by the side members of the frame. On the shaft is a spiral gear 27 which is driven by a spiral gear 28 mounted on the driving shaft 29. The shaft 29 is driven by this the part 44 is swung downward out of an electric motor, not shown. On the shaft 26 is also mounted a pinion 30 which meshes with a large gear 31, the latter being mounted on the crank shaft 32. The shaft 32 rotates at a substantially lower speed than the die carrier, say of the order of 200 ItRM.

On the crank shaft are mounted two crank arms 33 and 34 displaced angularly one from the other by 180. These arms move or reciprocate the wire back and forth for lapping the die. 7

As previously intimated, precision in the lapping operation is of the utmost importance. To accomplish this, an element such as a wire 35 is employed and is so mounted as.

to pass axially back and forth through the die and in so doing rub on the land and also on the approach. It is desirable for this purpose to use a stranded wire because the small interstices thereof will serve to retain the grinding material, such as diamond dust and oil for example. To properly guide the wire it is arranged to pass over two sheave pulleys 36 and 37 both of which are vertically adjustable in slotted brackets 38. In order that the approach of the die may be accurately formed, it is necessary to carefully locate the sheave 37 by raising or lowering it so that the angle which the wire makes with respect to a horizontal plane shall correspond to that of the approach. For this purpose a gauge 39 is provided and mounted on the right-hand bracket 38. The gauge comprises 35 two principal parts, a fixed part 40 having suitable scale markings 41 laid out in terms of approach angles of dies, and a movable part 42 which has a straight edge 43 whereby it may be properly aligned with the scale markings and a flat surface part 44 arranged to extend under the element or wire 35. The part 42. is pivotally mounted with respect to the part 40 and the two may be clamped or released by the knurled headed screw 45. The gauge is so set by hand with reference to the scale marking that the flat part 44 defines the proper angle for the wire after which the sheave 37 is raised or lowered until the wire 35 is parallel with the part 44. The sheave is then clamped in place. After contact with the wire. The sheave 36 is so set that the wire as it passes through the land is horizontal. The wire is detachably secured to the crank arms 33 and 34 by clamps 49. Included in the length of wire is a coiled extension spring 46 which with the crank arms serves to maintain a constant tension on the wire as it is moved back and forth by H the revolving shaft 32 and the crank arms 33 and 34. Since the crank arms are of the same length and displaced by 180, a movement of one arm in one direction is compensated for by an equal movement of the other arm 1n the opposite direction. This results in a constant tension of the spring and hence the latter is not subject to undue fatigue. For threading the Wire through the die, one of its end clamps is removed.

Reference has been made to grooves 9 being formed in the dies due to use as shown in Fig. 4. As it is not always possible to remove these grooves with the wire without too great a change in the die, I provide a quill 47, Fig. 7. The quill is made of suitable metal and has a barrel and also an end portion that is suitably tapered to conform to the desired shape of the approach of the die adjacent the land. The center of the quill is drilled to form a hole and the wall thereof makes a snug lit with the wire. The quill and wire are fastened together by a small set screw or equivalent means. To prevent the quill from rotating when it engages the rotating die, a guide 48 is provided. The quill is so set on the wire that on each movement of the wire to the left it will engage and rub the surface of the die as the latter rotates, there being suitable abrasive material applied to the inner end of the quill to cause it to lap the die at each inward stroke thereof. The tension on the wire is sufficient to insure this momentary contact on each inward stroke. As the quill retreats, the abrasive material has an opportunity to flow over the end portion preparatory to the succeeding stroke.

It will be observed that the wire 35 is always under constant tension and this is of great importance where extreme accuracy of results is desired. In other words, as the die is rotated, the wire exerts a uniform cutting or grinding action on the die both on the forward and backward strokes, as distinguished from an action where a change of tension means a greater cutting action on one stroke than in the other. Furthermore, a change of tension of the wire has a marked tendency to permit the wire to deviate from its predetermined path and thus modify the die shape to some extent. Since the die is rapidly rotated and the wire 35 reciprocated it follows that polishing is due to the combined movements of said parts and due to this all danger of wearing longitudinal grooves in the die is obviated.

On account of the relatively high speed of rotation of the die carrier, it is impractical to use plain or parallel bearings between it and the frame, and ball bearings for the purpose would of necessity have to be large which would unduly increase the size of the upper part of the machine as well as the cost. By using small rollers 21 mounted on small ball bearings, the advantage is obtained that the carrier can be rotated at the desired high speed without danger of injury to the bearings, and at the same time the size of the machine, particularly the upper part, can be kept within reasonable limits. Since the rollers are V-shaped and fit into correspond- IISJ ing grooves in the rings, they also serve to center the carrier and preserve the necessary radial clearances between the part 12 and the frame and also the side clearances between the fianges on the nuts 17 and the sides of the frame.

hat I claim as new and desire to secure by Letters Patent of the United States is:

1. I11 a machine of the character described, the combination of a frame, a die supporting means carried by the frame, means for rotating the supporting means and die, an element for polishing the die which passes through the opening therein, a crank shaft, and spaced crank arms secured to the shaft and diametrically opposed for moving the element back and forth through the die and maintaining constant tension thereon.

2. In a machine of the character described, the combination of a frame, a die supporting means carried by the frame, means for rotating the supporting means and die, an element for polishing the die which passes through the opening therein, adjustable guiding roller means for the element whereby the proper angle of approach of the die may be assured, a crank shaft, and diametrically op'posed crank arms on the shaft for maintaining the element under constant tension and also moving it back and forth through the die.

3. In a machine of the character described, the combination of a frame, a die supporting means carried by the frame, means for rotating the supporting means and die, an element for polishing the die which passes through the opening therein, brackets carried by the frame, adjustable guide rollers pivotally supported on the brackets, angularly displaced crank arms connected to the ends of the element for reciprocating it and maintaining it under tension, and a shaft for turning the arms.

l. In a machine of the character described,

the combination of a frame, a die supporting means carried by the frame, means for rotating the supporting means and die, an element for polishing the die which passes through the opening therein, a shaft, a pair of diametrically opposed crank arms secured to the shaft and connected to the ends of the element for reciprocating it, and a spring for maintaining a predetermined tension on the element.

5. In a machine of the character described, the combination of a frame, a die supporting means carried by the frame, gearing for rotating the die supporting means, an element for polishing the die which passes through the opening therein, a shaft, diametrically opposed cranks mounted on the shaft for reciprocating the element and maintaining a constant tension thereon, said cranks being connected to the ends of the element, gearing for rotating the shaft at a speed lower than that of the die supporting means, and a driving shaft which is common to said gearing.

6. In a machine of the character described, the combination of a frame, a die supporting means carried by the frame, means for rotating the supporting means and die, an element for polishing the die which passes through the opening therein, adjustable guide rollers over which the element moves, a gauge whereby'the angular relation of the element to the approach of the die may be determined, and means for maintaining the element under constant tension and also moving it back and forth through the die.

7. In a machine of the character described, the combination of a frame, a die supporting means carried by the frame, means for rotating the supporting means and die, an element for polishing the die which passes through the opening therein, a quill mounted on the element and moved thereby into successive engagements with the die to grind a surface thereof, and means for moving the element back and forth through the die and maintaining constant tension thereon.

8. In a machine of the character described, the combination of a frame, a die supporting means carried by the frame, means for rotating the supporting means and die, an element for polishing the die which passes through the opening therein, a quill mounted on the element and moved thereby into successive engagements with the die to grind a surface thereof, a means for preventing the quill from turning when moved into contact with the revolving die, a crank shaft, and a pair of angularly displaced crank arms secured to the shaft and attached to the element for reciprocating the element.

9. In a machine of the character described, the combination of a frame, a die supporting means mounted to revolve in the frame, a gear secured to the means, a grooved ring mounted on the supporting means to rotate therewith, a roller which engages the groove in the ring, and is supported by the frame, an abrasive carrying wire which passes through the opening in the die, a pair of sheaves for guiding the wire in its movements, a crank shaft and diametrically opposed crank arms for reciprocating the wire and maintaining it under constant tension, gearing for rotating the die supporting means and the crank shaft at different speeds, and a driving shaft which is common to the gearing.

10. In a machine of the character described, the combination of a frame, a die carrier, a gear for rotating the carrier, a grooved ring mounted to revolve with the carrier, and angularly spaced rollers which enter the groove in the ring and serve as a support and bearing means for the ring and carrier.

11. In a machine of the character described, the combination of a frame, a die carrierQa gear for rotating the carrier, a pair of V-shaped grooved rings, located one on each side of the gear, a set of angularly spaced rollers for each of the rings, said r011- ers entering the grooves in the rings, and ball bearing supports for the rollers carried by the frame.

In Witness whereof, I have hereunto set my hand.

7 GEORGE H. SITTNER. 

